JP6316698B2 - Internal spiral grooved tube, manufacturing method thereof and heat exchanger - Google Patents

Description

  The present invention relates to an internally spiral grooved tube, a manufacturing method thereof, and a heat exchanger.

In a fin tube type heat exchanger for an air conditioner or a water heater, a heat transfer tube for passing a refrigerant through an aluminum fin material is inserted to exchange heat. Conventionally, copper pipes have been used as heat transfer pipes, but due to demands for weight reduction, cost reduction, and recyclability improvement, replacement with aluminum alloy pipes is required.
In recent years, air conditioners have been improved in heat transfer characteristics for energy saving, and refrigerants have been reviewed and the structural design of heat exchangers has been improved. Among them, heat transfer tubes, which are one of the components, are required to have higher performance. At present, an inner grooved tube having a spiral groove continuous on the inner surface is mainly used, and the heat exchange efficiency is improved.

  As a method for producing an internally spiral grooved tube, there is known a groove rolling method (Patent Document 1) in which a twisted groove is rolled while being rolled on the inner surface of the tube. In conventional copper pipes, a groove rolling method is adopted in which the pipe is pressed against a grooved plug provided on the inner circumference of the pipe with a ball bearing that rotates at high speed from the outer circumference of the pipe, and a twisted groove is rolled on the inner surface of the pipe. Similarly, the groove rolling method is being used to make the grooved tube aluminum.

In addition, as another manufacturing method of the inner surface spiral grooved tube, a raw tube having a straight groove is used on the inner surface, and the raw tube is drawn while being reduced in diameter with a drawing die while being twisted before entering the drawing die. There is known a method of manufacturing an internally spiral grooved tube having a twist angle by plastically flowing the reduced diameter portion (see Patent Document 2).
As another manufacturing method, an element tube in which a plurality of linear grooves along the length direction are formed on the inner surface at intervals in the circumferential direction is wound in a coil shape, and the coil element tube is placed on the coil axis. A method is known in which an inner spiral grooved tube is manufactured by applying a constant tension along the straight line and stretching the tube into a straight tube to twist the element tube (see Patent Document 3).

Japanese Patent Laid-Open No. 06-190476 JP-A-10-166086 JP 2012-236225 A

However, it is difficult to obtain a predetermined groove shape by the groove rolling method shown in Patent Document 1 in manufacturing an internally spiral grooved tube using an aluminum alloy.
An example of a production apparatus for carrying out the groove rolling method is shown in FIG. The manufacturing apparatus includes a holding die 51 for pulling out the raw tube 50, a holding plug 52 inside the holding die 50, and a finishing die 53 on the downstream side of the holding die 51. A rolling ball 55 is provided between the holding die 51 and the finishing die 53, and a grooved plug 57 is provided inside the position where the rolling ball 55 is provided via a connecting shaft 56 extending from the holding plug 52. Is provided. In this manufacturing apparatus, the diameter of the raw tube 50 is reduced by the holding plug 52 and the holding die 51, and the spiral groove 58 is formed on the inner peripheral surface of the raw tube 50 while pressing the raw tube 50 against the grooved plug 57 with the rolling ball 55. Drawing is performed while rolling, and an internally spiral grooved tube is manufactured by the finishing die 53.
Since the aluminum alloy has a lower strength than the copper alloy, in order to obtain a pressure resistance with the inner spiral grooved tube, it is necessary to increase the bottom wall thickness of the tube compared to the copper inner spiral grooved tube. In order to make plastic flow difficult, it is difficult to roll so-called high slim type fins with a predetermined inner surface groove shape, especially high fin height and narrow fin width. It is easy to produce. Therefore, if it is forcibly processed by the groove rolling method, the tube will buckle or break. In addition, aluminum flaws are generated by contact between the groove plug provided on the inner peripheral side and the inner peripheral side of the pipe, reducing the accuracy of the groove shape during processing, or remaining difficult to remove after processing and clogging the groove. There are problems such as increasing heat transfer characteristics and pressure loss. Further, in the groove rolling method, when a floating plug is inserted in advance, the groove rolling lubricant is filled on the inner peripheral side of the pipe. As a result, the bottom wall thickness and groove shape of the manufactured internally spiral grooved tube change between the head and the buttocks in the longitudinal direction, and the variation in the groove shape is large. The variation in the bottom wall thickness and the groove shape affects the thermal characteristics and causes variation in the expansion ratio in the expansion of the pipe that joins the fin and the inner surface spiral groove tube.
Furthermore, when CO ₂ is used as the refrigerant of the heat exchanger, it is necessary to employ a heat transfer tube having a high pressure resistance. Although the pressure resistance strength of the heat transfer tube can be increased by increasing the bottom wall thickness, as described above, it is difficult to cope with this by the groove rolling method.

For this reason, in order to manufacture the inner surface spiral grooved tube made of an aluminum alloy, a manufacturing method other than the groove rolling method is required.
As shown in FIG. 19, the manufacturing apparatus described in the above-mentioned Patent Document 2 supports the operation drum 102 on a rotating shaft 101 that is horizontally supported so as to be rotatable around an axis by two support members 100 of a column type. The raw tube 103 wound around the operation drum 102 in a coil shape is pulled out via the pulling die 105 and then wound around the winding drum 106.
A plurality of straight grooves are formed on the inner peripheral surface of the raw tube 103, and the raw tube 103 that has passed through the drawing die 105 is formed into an inner spiral grooved tube 108 having a spiral groove on the inner surface.

  In FIG. 19, reference numeral 110 denotes a driving device such as a motor for rotating the rotating shaft 101, and the output shaft of the driving device 110 rotates to the 9 end side of the rotating shaft 101 via a transmission device 111 such as an endless belt. To communicate. Although simplified in FIG. 19, the rotating shaft 101 is configured as a part of a frame-like frame, and the operation drum 102 is rotatably supported by the rotating shaft 113 inside the frame. . A roller (not shown) for guiding the raw tube 103 is provided on the distal end side of the rotating shaft 101, and the movement trajectory of the raw tube 103 is changed via this roller, and the drawing die 105 installed on the gantry 115 is pulled out. The core tube 103 can be pulled out after the core tube 103 is aligned with the hole.

The manufacturing apparatus shown in FIG. 19 uses an extraction die 105 to reduce the diameter of the raw tube 103 while twisting, thereby generating a plastic flow in the reduced diameter portion of the raw tube 103 to form an inner spiral grooved tube having a large twist angle. It is known as a device that can be manufactured.
However, in the manufacturing apparatus shown in FIG. 19, since the twist is applied to the element tube 103 in the middle from the position where the element tube 103 is fed from the operation drum 102 to the drawing die 105, a large twist angle is given. Is difficult. In other words, it is difficult to apply both twisting and shrinking forces to the inside of the drawing die 105 in a well-balanced manner. For this reason, the torsional force concentrates on the position of the front end side of the rotary shaft 101 and the front and rear positions thereof, for example, where the movement path of the raw tube 103 has been changed from the position where it is drawn from the operation drum 102 to the drawing die 105. However, there is a problem that the base tube 103 is easily buckled before reaching the die 105.

Moreover, the manufacturing apparatus described in the above-mentioned Patent Document 3 causes a certain twist in a raw tube in which a plurality of linear grooves along the length direction are formed on the inner surface at intervals in the circumferential direction, and on the inner surface. FIG. 20 shows an outline of an apparatus for producing an internally spiral grooved tube having a spiral groove.
The manufacturing apparatus 120 shown in FIG. 20 is formed in a coil shape by winding means 123 that winds up a tube 121 having inner fins formed on the inner surface by a plurality of linear grooves on the circumference of the winding roll 122. The coiled tubular material 121a is stretched toward the front side in the extension direction of the coil axis 124, and is formed into a straight tube. A pulling die (not shown) for correcting the cross-sectional shape of the tubular body after the pulling, and a correction And a heat treatment means for heating the inner spiral grooved tube. Note that the manufacturing apparatus 120 shown in FIG. 20 is used in a plurality of stages connected in series according to the required twist angle.

In the manufacturing apparatus 120, a feed roll 125 and a restraining roll 126 for feeding the coiled tubular material 121a are provided outside the winding roll 122, and a guide plate 127 for restraining the coiled tubular material 121a is provided. Moreover, a heater is incorporated in a part of the holding roll 126, and the coiled tube material 121a can be heated to a temperature (200 to 300 ° C.) necessary for processing.
The tension means 130 is provided with a plurality of stretchers 128 for chucking and extending the coiled tubular material 121a, and a plurality of pinch rolls 129 for forming a straight tube while applying tension to the expanded tubular material. The inner spiral grooved tube 132 is wound around the take-up roll 131.

  The raw material pipe 121 made of aluminum or aluminum alloy is processed into a coiled pipe material 121a by the manufacturing apparatus 120 shown in FIG. 20, and is stretched by a stretcher 128 and formed into a straight tube shape by a pinch roll 129, thereby providing a straight groove on the inner surface. The inner tube 121 can be processed into a spiral grooved tube 132 having a spiral groove on the inner surface and wound.

However, when an internally spiral grooved tube is manufactured by the manufacturing apparatus 120 shown in FIG. 20, the obtained twist angle depends on the diameter of the take-up roll 122, and the diameter is reduced to apply a large twist in a single process. There is a need. However, when a hollow tube is wound around a roll having a small diameter, the tube is flattened or buckled. Therefore, it is necessary to repeat the process of winding to a large diameter and stretching a plurality of times, which is not productive. In addition, since the tube is work-hardened in the step of winding on a roll and the step of drawing, there is a problem that a heat treatment step is required to remove this work-hardening and the manufacturing time becomes longer.
In addition, as described above, the torsion angle to be applied greatly affects not only the diameter of the roll to be wound, but also the pitch when being wound into the coil shape, but it is difficult to process into a spring shape with a constant pitch. As a result, there is a problem that the twist angle varies greatly in the longitudinal direction, and a stable twist angle cannot be provided. Since this is repeated a plurality of times, the variation in the twist angle tends to be further increased.

As a result of studying various conventional manufacturing methods, the present inventor has found that a method of directly twisting an element tube having a straight groove in advance is suitable for manufacturing a heat transfer tube made of aluminum and an aluminum alloy. thinking. Extrusion is suitable for the production of a raw pipe having a straight groove, and a high slim fin type groove shape having a narrow fin apex angle and a high fin height and excellent heat exchange characteristics can also be formed.
However, the manufacturing methods described in Patent Document 2 and Patent Document 3 have various problems as described above.

In addition, if the crystal grain structure exceeds the range of the crystal grain size of the raw tube, the crystal grain size of the manufactured inner spiral grooved tube becomes coarse, and when the tube is expanded, an orange peel with rough skin like an orange peel is applied to the outer peripheral surface. And unevenness occurs on the surface.
When the heat transfer tube is assembled in a heat exchanger, a heat expansion tube having a diameter larger than that of the heat transfer tube is inserted into the heat transfer tube to expand the diameter of the heat transfer tube and mechanically joined to the aluminum alloy radiating fin. Since the joint surface between the heat radiating fin and the heat transfer tube is reduced due to unevenness caused by rough skin on the outer periphery of the tube and the joining rate is lowered, the thermal characteristics deteriorate.

  Another problem is due to rough skin on the inner circumference side of the pipe, and when viewed in a vertical cross section in the longitudinal direction of the heat transfer pipe, the fins that are originally formed in the bottom thick part in the center direction of the circle are It is a problem that the fin collapse is amplified when the tube is expanded by the tube expansion plug due to the unevenness of the surface. In that case, the force acting in the outer peripheral direction from the tube expansion plug is absorbed by the fin collapse and is difficult to be transmitted to the bottom wall thickness part, so that the predetermined tube expansion rate cannot be obtained, and the heat radiation fin and the heat transfer tube Sufficient bonding cannot be obtained, leading to deterioration of thermal characteristics. Further, when the degree is severe, fin collapse becomes large and the refrigerant flow path is blocked, and the thermal characteristics are greatly deteriorated. Note that such fin collapse tends to become more prominent when the bottom wall thickness of the heat transfer tube increases.

  These orange peels are not only generated on the surface of the heat transfer tube when the tube is expanded, but also when the crystal grain size of the raw tube used for manufacturing the heat transfer tube is large, it is generated during the manufacture of the heat transfer tube, and irregularities are formed on the outer and inner peripheral surfaces. Therefore, it is necessary to limit not only the crystal grain size in the crystal grain structure of the manufactured internally spiral grooved tube but also the crystal grain size of the raw pipe used. Furthermore, the manufactured inner surface spiral grooved tube is work-hardened as it is, and as it is, only the groove is easily crushed by expanding the tube, so annealing for making O material is necessary. Since it grows, regarding the heat transfer tube, it is necessary to set a limit on the crystal grain size after the final heat treatment.

  The present invention relates to an internally spiral grooved tube obtained by directly twisting an aluminum or aluminum alloy element tube having a straight groove on its inner surface, and has a thick bottom wall, a high fin height, and a fin top. An object of the present invention is to provide an inner spiral grooved tube having a narrow angle and no generation of orange peel at the time of processing and expanding the inner spiral grooved tube, and having excellent tube expandability and inner surface properties.

The inner surface spiral grooved tube according to the present invention is directly formed on an aluminum base tube in which a plurality of linear grooves along the length direction are formed on the inner surface at intervals in the circumferential direction, and fins are formed between the linear grooves. An inner spiral grooved tube manufactured by applying a twisting process, wherein a bottom wall thickness of the inner spiral groove tube in the plurality of spiral grooves is 0.55 mm or more, and the fin from the spiral groove The fin apex angle expressed by the relative angle between the two side wall surfaces of the fin when the fin is sectioned is 25 ° or less, and the average grain size in the crystal grain structure is 0.24 mm or more. Is 120 μm or less, and the variation in the twist angle of the groove varies within a range of ± 1 ° or less in any measurement range of 1 m to 5 m in length .
According to such a structure, when manufacturing an internally spiral grooved tube by a method of directly twisting the raw tube having a straight groove on the inner surface as a starting material, the bottom wall thickness is large. It is possible to provide an internally spiral grooved tube that is high in height, has a narrow fin apex angle, does not generate orange peel during processing and expansion of the internally spiral grooved tube, and has excellent tube expandability and internal surface properties.
In addition, since the variation in the twist angle of the groove is ± 1 ° or less, it is possible to provide an internally spiral grooved tube with stable heat conduction efficiency over the length direction.
In the inner spiral grooved tube, the bottom wall thickness may be 0.65 mm or more.
In the above-mentioned inner surface spiral grooved tube, the height of the fin may be 0.5 mm or more.

  In the inner spiral grooved tube, the raw tube may be an extruded raw tube having a bottom wall thickness of 0.55 mm to 0.9 mm.

  By the way, in the above-mentioned groove rolling method, since a floating plug is inserted into the inner surface of the tube to roll the groove, it has been difficult to apply to a heat transfer tube having an outer diameter of φ5 mm or less. After forming the groove by the groove rolling method, it is possible to reduce the diameter to 5 mm or less by drawing, but the entire tube is stretched in the longitudinal direction by drawing, and the added twist angle becomes shallow accordingly. End up. Therefore, there is a problem that a thin tube and a high twist angle cannot be compatible. The embodiment according to the present invention can solve such a problem.

The inner surface spiral grooved tube is formed by directly twisting an aluminum base tube in which a plurality of linear grooves along the length direction are formed on the inner surface at intervals in the circumferential direction, and fins are formed between the linear grooves. An inner spiral grooved tube manufactured by providing an outer diameter of φ5 mm or less, a groove twist angle of 20 ° or more and 40 ° or less, and an average grain size of 120 μm or less in a crystal grain structure In any measurement range of 1 m to 5 m in length , variation in the twist angle of the groove may vary within a range of ± 1 ° or less.

According to the present invention, an inner spiral grooved tube having an outer diameter of 5 mm or less and a groove twist angle of 20 ° or more can be provided because it can be manufactured by directly twisting the raw tube. When this inner surface spiral grooved tube is used as a heat exchanger tube of a heat exchanger, by setting the twist angle of the groove to 20 ° or more, the internal surface area through which the refrigerant flows can be increased, and the thermal characteristics are improved. . Moreover, by setting it as (phi) 5 mm or less, while the freedom degree in the design of a heat exchanger increases, it can contribute to size reduction, and it becomes possible to arrange | position a small-diameter heat exchanger tube at high density.
In addition, when the average crystal grain size of the metal structure is 120 μm or less, even if it is a small diameter such as a heat exchanger tube for a heat exchanger, it does not cause rough skin like an orange peel, and has excellent surface properties. It is possible to provide an inner surface spiral grooved tube whose inner surface side groove shape can also be a desired shape.
Moreover, since it is excellent in surface property, when it assembles | assembles to a heat exchanger with a fin, it can provide an internal spiral grooved tube which cannot produce the joining defect of a fin, a fin fall, etc. easily.

  Further, in the above-described inner surface spiral grooved tube, the variation in the bottom wall thickness may be ± 1% or less.

  Further, in the above-mentioned inner surface spiral grooved tube, the variation in fin height may be ± 1% or less.

  Further, in the inner spiral grooved tube described above, the variation in outer diameter may be ± 1% or less.

  In the inner spiral grooved tube, the average grain size of 120 μm or less may be an average grain size achieved after annealing.

  Further, in the above-mentioned inner surface spiral grooved tube, the fin tilt angle of the fin formed along the inner surface spiral groove may be 1 ° or less.

  In the inner spiral grooved tube described above, it is preferable that the outer surface has no orange peel defined as a step having a surface roughness (Rmax) exceeding 15 μm.

  Further, in the above-mentioned inner surface spiral grooved tube, in the inner surface spiral grooved tube, as for the crystal grain structure of the raw tube used for the production, all of the metal structure is outside the fibrous structure or the surface layer along the length direction of the tube. 5% or less of the thickness of each inner circumference may be a recrystallized structure and all other parts may be a fibrous structure, or the average crystal grain size of the metal structure may be 80 μm or less.

  In the manufacturing method according to the inner surface spiral grooved tube, a plurality of linear grooves along the length direction are formed on the inner surface at intervals in the circumferential direction, and an aluminum base tube in which fins are formed between the linear grooves is coiled. The unwinding side capstan is rotated by rotating the drum and the unwinding side capstan along an axis perpendicular to the winding axis of the drum while unwinding from the drum held in the shape and winding the unwinding side capstan on the unwinding side capstan. A raw tube unwinding step of unwinding the raw tube while rotating it about the axis, and passing the unwound raw tube through a drawing die to give a twist while reducing the diameter, A twisting and pulling step, wherein the straight groove is a spiral groove, the fin is spiral, a bottom wall thickness of the plurality of spiral grooves is 0.55 mm or more, and the height of the fin from the spiral groove is The fin apex angle expressed by the relative angle between the two side wall surfaces of the fin when the fin is cross-sectioned is 25 ° or less, the average grain size is 120 μm or less in the crystal grain structure, and A manufacturing method of an internally spiral grooved tube, characterized in that the variation of the twist angle of the groove is ± 1 ° or less.

  In order to manufacture the inner surface spiral grooved tube, the manufacturing method according to the above inner surface spiral grooved tube preferably uses a raw tube having a bottom wall thickness of 0.55 mm or more and 0.9 mm or less.

  In the manufacturing method according to the inner surface spiral grooved tube, a plurality of linear grooves along the length direction are formed on the inner surface at intervals in the circumferential direction, and an aluminum base tube in which fins are formed between the linear grooves is coiled. The unwinding side capstan is rotated by rotating the drum and the unwinding side capstan along an axis perpendicular to the winding axis of the drum while unwinding from the drum held in the shape and winding the unwinding side capstan on the unwinding side capstan. A raw tube unwinding step of unwinding the raw tube while rotating it about the axis, and passing the unwound raw tube through a drawing die to give a twist while reducing the diameter, A twisting and pulling step, wherein the straight groove is a spiral groove, the fin is spiral, the outer diameter is 5 mm or less, the twist angle of the groove is 20 ° or more and 40 ° or less, and the average grain size in the grain structure Characterized by the size and 120μm or less.

As in the technique disclosed in Patent Document 2, simply sending the raw tube from the coil and passing the drawing die as it is, the distance of the processing area until the raw tube unwound from the coil enters the drawing die is long. In the meantime, kinking occurs as if locally bent, and the element tube tends to buckle, so that a large twist cannot be applied.
When manufacturing an internally spiral grooved tube, the unwinding side capstan is wound around the unwinding side capstan before the drawing die, and the unwinding side capstan is rotated in synchronization with the unwinding side drum. The axis of the processing area to be added can be shifted from the unwinding path of the tube from the unwinding drum by the number of turns of the tube wound around the capstan in a direction parallel to the rotation axis of the capstan and wound around the capstan. By being constrained, it is possible to control the length of the work zone where the pipe is twisted to a constant range within a shorter range from the top position of the unwinding capstan to the end of the drawing die. Speed and revolving speed of unwinding side capstan (revolution here means the rotation of unwinding side capstan around the processing area axis) and reduction ratio by drawing By controlling it, a constant twist angle can be given stably in the longitudinal direction of the tube, and the distance between the capstan and the drawing die in front of the drawing die is adjusted, both distances are made relatively short, and the diameter reduction rate By increasing the value, it is possible to suppress the occurrence of buckling even when a large twist angle is imparted by processing by one unwinding.

  Furthermore, when unwinding from the drum, if the drum shaft rotation has a function of applying a rear tension with a brake device such as a powder brake and providing a pull-out side capstan to provide the front tension, Appropriate tension can be stably applied, so that there is no slack in the raw pipe pass line, and the raw pipe enters the drawing die without being misaligned, thereby preventing occurrence of uneven thickness and buckling. Regarding the misalignment when the raw tube enters the drawing die, the effect of suppressing the misalignment is also obtained by restraining the raw tube with a capstan before and after the drawing die.

The twist angle of the inner spiral groove tube to be manufactured can be controlled by the relationship between the drawing speed of the raw pipe and the revolution speed of the unwinding capstan. Increasing the speed increases the twist angle.
In addition, unlike the rolling method, it is not necessary to roll a groove by inserting a plug inside the round tube of the cocoon, so by forming a deep groove in the inner wall of the raw tube before twisting in advance, this manufacturing method Can manufacture high slim fin type pipes with high fin heights and small fin apex angles with high accuracy and ease of manufacturing, eliminating the need to clean the inner surface of the pipe material after machining the pipes, reducing man-hours. it can. The raw tube in which the straight groove is formed can be easily obtained by, for example, extrusion.

  In the manufacturing method according to the above-mentioned inner surface spiral grooved tube, as the element tube, a fibrous structure along the length direction of the tube or a surface layer of only 5% or less of the thickness of each outer and inner circumference is a recrystallized structure. Except that, it may be a fibrous structure, or an extruded element tube having an average crystal grain size of a metal structure of 80 μm or less may be used.

In the manufacturing method according to the inner spiral grooved tube, the diameter reduction rate by the drawing die may be 5 to 40%.
When the drawing process and the twisting process are combined, the value of the maximum twist angle (hereinafter referred to as a limit twist angle) that can be twisted without causing buckling increases. When only the twisting process is performed on the raw pipe, shear stress is applied in the circumferential tangent direction of the raw pipe, and the raw pipe is twisted. At that time, a compressive stress acts on the longitudinal direction of the raw pipe. This compressive stress increases as the torsional angle increases, and buckling occurs when the compressive stress exceeds the buckling stress that causes buckling. Drawing has the effect of reducing this compressive stress by applying tensile stress in the longitudinal direction of the tube by drawing, and can suppress the occurrence of buckling.
In the test by the present inventors, a result that the limit twist angle is improved as the diameter reduction rate is increased is obtained.
When the diameter reduction rate is too small, the effect of tensile stress by drawing is small, and it is difficult to obtain a large twist angle. On the other hand, if the diameter reduction rate becomes too large, the raw tube may be broken, so it is preferable to set it to 40% or less.

  In the manufacturing method according to the inner spiral grooved tube, a position where the raw tube starts to be wound around the unwinding side capstan and a position where the raw tube starts to be fed from the unwinding side capstan to the drawing die side are By shifting in a direction parallel to the rotation axis of the unloading capstan, the space between the unwinding capstan and the drawing die may be used as a twisting region of the raw tube.

  The manufacturing method according to the inner spiral grooved tube may apply a front tension and a rear tension to the tube when the diameter of the tube is reduced while twisting the tube through the tube.

  In the manufacturing method according to the above inner spiral grooved tube, the inner spiral grooved tube that has passed through the drawing die may be wound around a drawing side capstan.

  In the manufacturing method according to the inner spiral grooved tube, the inner spiral groove tube unwound from the drawing-side capstan may be shaped with a second drawing die.

  In the manufacturing method according to the inner spiral grooved tube, the raw tube unwound from the drum may be shaped into a perfect circle by a drawing die before reaching the unwinding capstan.

  The heat exchange fin according to the inner spiral grooved tube is characterized in that the inner spiral grooved tube and the fin are integrated.

  According to the present invention, when manufacturing an internally spiral grooved tube by using a raw material tube having a straight groove on the inner surface as a starting material and directly twisting the raw material tube, the bottom wall thickness is thick and the fin height is increased. Therefore, it is possible to provide an inner spiral grooved tube having a high fin angle, a narrow fin apex angle, no orange peel at the time of processing and expanding the inner spiral grooved tube, and excellent tube expandability and inner surface properties. In addition, since the variation in the twist angle of the groove is ± 1 ° or less, it is possible to provide an internally spiral grooved tube with stable heat conduction efficiency over the length direction.

The schematic diagram which shows one Embodiment of the manufacturing apparatus of the internal spiral grooved pipe which concerns on this invention. The principal part expansion explanatory drawing of the manufacturing apparatus. The top view which shows typically the winding state of the raw tube with respect to the unwinding side capstan of the manufacturing apparatus. Sectional drawing of the drawing die used for the manufacturing apparatus. It is a figure explaining the element | tube with the linear groove | channel formed in the inner surface, (a) is a front view, (b) is a sectional side view. Explanatory drawing which shows the state which expand | deployed the cross section and a part of pipe | tube with an inner surface spiral groove in which the spiral groove was formed in the inner surface. An example of the heat exchanger provided with the internal spiral grooved tube which concerns on this embodiment is shown, (a) is a side view, (b) is a perspective view. The graph which shows the relationship between the process area length at the time of manufacturing an internal spiral grooved tube in an Example, and a limit twist angle. The graph which shows the relationship between the diameter reduction rate at the time of drawing | extracting at the time of manufacturing an internal spiral grooved pipe | tube in an Example, and a limit twist angle. The graph which shows the revolution speed of the unwinding side capstan at the time of manufacturing an internal spiral grooved pipe | tube in an Example, and the pipe diameter of a twist angle. The graph which shows the relationship between the length direction measurement position of an example of the internal spiral grooved pipe manufactured in the Example, and a twist angle. The figure which shows the fin apex angle and fin top width in the internal spiral grooved pipe manufactured in the Example. Explanatory drawing which shows the fin fall angle in the internal spiral grooved pipe manufactured in the Example. Sample No. as an example. 7 shows the inner spiral grooved tube obtained in step 7, (a) is a metal structure photograph of a partial cross section of the inner spiral groove tube, (b) is a spiral groove by cutting a part of the inner spiral groove tube (C) is a photograph showing a state where the inner surface spiral grooved tube is cut obliquely, and (d) is a photograph showing a groove shape of a partial cross section of the inner surface spiral grooved tube. Sample No. as a comparative example. Fig. 8 shows the inner spiral grooved tube obtained in Fig. 8, (a) is a metallographic photograph of a partial cross section of the inner spiral groove tube, (b) is a part of the inner spiral groove tube cut open the spiral groove The development photograph which shows the shown state, (c) is a photograph which shows the groove shape of the partial cross section of an internal spiral grooved tube. Sample No. 7 and sample no. 8 shows the state of occurrence or non-occurrence of orange peel in the inner surface spiral groove tube of FIG. 8, (a) is a photograph showing the surface state of the inner surface spiral groove tube of the embodiment in which no orange peel is generated, (b) is orange The photograph which shows the surface-like body of the internal spiral grooved tube of the comparative example in which the peel has generate | occur | produced. Sectional drawing of the apparatus for enforcing a groove rolling method. The cross-sectional photograph which shows an example of the internal spiral grooved pipe manufactured with the apparatus shown in FIG. The block diagram which shows an example of the conventional apparatus for manufacturing an internal spiral grooved tube using a drawing die. The block diagram which shows an example of the apparatus which manufactures an internal spiral grooved pipe | tube by winding after extending | stretching a raw pipe | tube around the outer periphery of a drum.

Hereinafter, an embodiment of a manufacturing method and a manufacturing apparatus of an inner spiral grooved tube according to the present invention will be described with reference to the drawings.
In addition, in order to make the characteristics of the present invention easy to understand, the manufacturing apparatus and the inner surface spiral grooved tube shown in each drawing may be shown by enlarging the main part, and the dimensional ratios of the respective components are It is not always the same as actual.
In the manufacturing device A for the inner surface spiral grooved tube of the present embodiment, the raw tube 11 (see FIG. 5) in which a plurality of linear grooves 11a along the length direction are formed on the inner surface at intervals in the circumferential direction is fixed. This is an apparatus for producing an inner surface spiral grooved tube 11R (FIG. 6) having a spiral groove on the inner surface by causing twisting.

The inner spiral grooved tube 11R is made of, for example, the international aluminum alloy standard 3000 series and is not particularly limited in the present invention, and may be made of any aluminum alloy or pure aluminum. In the present embodiment, the term “made of aluminum alloy” includes any aluminum alloy or pure aluminum.
Regarding the shape of the inner spiral grooved tube 11R, the outer diameter is 1.5 mm or more and 5 mm or less, preferably less than 5 mm. In addition, the inner spiral grooved tube 11R has a plurality of, for example, 30 to 60 convex spiral fins 11c and a plurality of, for example, 30 to 60, concave spiral grooves 11d on its inner peripheral surface.
Further, in the inner surface spiral grooved tube 11R, as shown in FIG. 13, the height t (see FIGS. 12 and 13) of the spiral fin 11c is 0.24 mm or more, and the fin apex angle θ ₁ (see FIGS. 12 and 13). ) Is 25 ° or less, and the bottom thickness d (the thickness of the tube at the bottom of the spiral groove, see FIG. 13)) is 0.55 mm or more. The size of the groove inner bottom corner R of the spiral groove 11d is 0.15 mm or less, more preferably the size of R is 0.08 mm or less. Further, the twist angle θ of the spiral fin 11c is set to 15 to 30 °. In the inner spiral grooved tube 11R shown in FIG. 6, the twist angle θ is grasped as the inclination angle of the spiral groove 11d in the diameter length a and the twist cycle b of the inner spiral groove tube 11R.
Further, the twist angle θ of the groove of the inner spiral grooved tube 11R is set to 20 ° to 40 °, and the variation of the twist angle θ is set to ± 1 ° or less. Further, in the inner spiral grooved tube 11R, the variation of the bottom wall thickness d is ± 1% or less, the variation of the fin height h is ± 1% or less, and the variation of the outer diameter is ± 1% or less.

  As described above, it is preferable that the outer diameter of the inner spiral grooved tube 11R be φ1.5 mm or more. When the outer diameter is less than φ1.5 mm, it is difficult to maintain a bottom wall thickness d of 0.3 mm or more, and the pressure resistance is reduced. Further, if the outer diameter is less than φ1.5 mm, the flow path through which the refrigerant flows becomes narrow and the pressure loss increases, which is not preferable.

By setting the height t of the spiral fin 11c to 0.24 mm or more, the fin apex angle θ ₁ to 25 ° or less, and the bottom wall thickness d to 0.55 mm or more, the inner surface spiral grooved tube 11R becomes the heat transfer tube of the heat exchanger. It is possible to improve both the evaporation performance and the condensation performance of the refrigerant. A more preferable height t of the spiral fin 11c is 0.26 mm or more and 0.30 mm or less, a more preferable fin apex angle θ ₁ is 8 ° or more and 20 ° or less, and a more preferable bottom wall thickness d is 0.6 mm or more and 0. .75 mm or less.

  Since the raw tube 11 is drawn to be processed into an inner spiral grooved tube 11R as will be described later, it is preferable to use a pipe body having an outer diameter larger by about 5 to 50% than the inner spiral grooved tube 11R. . The raw tube 11 has substantially the same cross-sectional shape as the inner spiral grooved tube 11R. The element tube 11 is a fibrous structure in which the metal structure is all along the length direction of the tube, or 5% or less of the thickness of the surface layer is a recrystallized structure on the outer periphery and the inner periphery, respectively. Other than the above, all are made into a fibrous structure or a crystal grain having an overall average grain size of 80 μm or less.

  As shown in FIG. 1, the manufacturing apparatus A includes a drum 21 that holds an element tube 11 in which fins 11 b are formed by linear grooves 11 a on an inner surface in a coiled state, and an element that is unwound from the drum 21. While winding the tube 11, the unwinding-side capstan 22 that unwinds the raw tube 11, and the drum 21 and the unwinding-side capstan 22 rotate around an axis C perpendicular to the winding shaft 21 a of the drum 21. Pulling out while winding the means 23, the drawing die 24 through which the raw pipe 11 fed from the unwinding side capstan 22 passes, and the inner spiral grooved tube 11R through which the linear groove on the inner surface becomes a spiral groove through the drawing die 24 A second drawing die 26 for passing the side capstan 25, the inner spiral grooved tube 11R via the drawing side capstan 25, and the second drawing die A third capstan 27 for winding the inner surface helical grooved pipe 11R passing through the die 26, and a winding drum 29 for winding the third inner surface helical grooved pipe 11R unwound from the capstan 27.

  An unwinding drum (hereinafter referred to as unwinding drum) 21 is attached to the first frame 32 together with a guide pulley 31 and a support shaft 31a for guiding the unwinded tube 11 along the axis C. ing. In this case, the unwinding drum 21 is rotatably supported by the first frame 32 and feeds the raw tube 11 with a constant tension while controlling the braking force by the winding diameter. Reference numeral 33 denotes a cover that integrally covers the unwinding drum 21, the guide pulley 31, and the like. In the structure shown in FIG. 1, the brake force of the drum 21 is generated by a brake device 15 such as a powder brake capable of adjusting torque, which is provided so as to be connected to the winding shaft 21a.

Further, the front end portion 34 and the rear end portion 35 of the first frame 32 extend axially along the axis C, and the front end portion 34 and the rear end portion 35 are provided with two leg portions 37 via a bearing 36. Therefore, the first frame 32 is rotatable by being supported horizontally and rotatable about the axis. The front end portion 34 of the first frame 32 protrudes forward from the leg portion 37, and the second frame 38 that holds the unwinding side capstan 22 is fixed to the protruding end portion. Accordingly, the second frame 38 is fixed with respect to the first frame 32 and is supported so as to be rotatable about the axis C together with the unwinding capstan 22.
The first frame 32 includes a rectangular frame-shaped main frame 32a that supports the winding shaft 21a of the drum 21, and a side frame isosceles trapezoidal sub-frame 32b that extends from one side of the main frame 32a. And a shaft-type front end portion 34 formed to extend to the front end side of the sub-frame 32b and a shaft-type rear end portion 35 formed to extend to the rear end side of the main frame 32a.
The front end portion 34 of the first frame 32 protrudes further forward than the one leg portion 37, and a second frame (unwinding side frame) 38 that holds the unwinding side capstan 22 is fixed to the protruding end portion. Has been. Therefore, the second frame 38 is integrated with the first frame 32, and is supported together with the unwinding side capstan 22 so as to be rotatable around the axis about the horizontal axis C.

The rear end portion 35 of the first frame 32 protrudes rearward from the leg portion 37, and a drive unit 39 such as a motor is provided below the protruding end portion. One end of a transmission device 39 a such as an endless belt is wound around the rotation shaft of the drive unit 39, and the other end of the transmission device 39 a is wound around the protruding end of the rear end portion 35. For this reason, the rotational force of the rotating shaft of the drive part 39 can be transmitted to the protruding end of the rear end part 35, and the first frame 32 and the second frame 38 can be rotated.
The drive unit 39 rotates the first frame 32 and the second frame 38 integrally. The drive unit 39, both the frames 32 and 38, the bearing 36, the leg portion 37, and the like provide the unwinding drum 21 and the unwinding side. Rotating means 23 is configured to rotate the capstan 22 integrally around the axis C.

In the illustrated example, the unwinding side capstan 22 includes a driven roller 41. The unwinding capstan 22 is wound around the unrolled roller 41 so as to be wound around a plurality of turns along the axis C again. I am trying to send it out. As shown in FIG. 3, the tube 11 is wound around the capstan 22 by several turns so that the unwinding path from the unwinding drum 21 is parallel to the rotation axis of the capstan 27. It is sent out along a shifted axis (axis of the machining area described later) C1. Since the raw tube 11 is wound several times, it is unwound with a stable tension.
2 mainly shows the relative relationship between the unrolled tube 11 and the unwinding side capstan 22 and the drawing side capstan 25 provided before and after the drawing die 24 in the manufacturing apparatus A shown in FIG. FIG. 2 is a drawing, and FIG. 2 omits the driven rollers 41 and 43.
Further, as shown in FIG. 2, a region having a length L between the top position of the capstan 22 and the outlet portion of the drawing die 24 is a processing region.

In this case, the driven roller 41 is provided at a position retracted from the axis C (the travel path of the raw tube 11), and in the illustrated example, the axis C (element) with respect to the unwinding side capstan 22 is provided. It is arranged so as to be perpendicular to the travel path of the tube 11. Further, the capstan 22 and the driven roller 41 are not parallel to each other, and are arranged in a direction in which the axis of the driven roller 41 intersects the axis of the capstan 22. It is possible to prevent overlapping of the wound raw tubes and effectively suppress the occurrence of surface scratches, breakage, and buckling of the internally spiral grooved tube to be produced.
Further, a drawing die 16 for recovering the perfect circle of the raw tube 11 before twisting is provided in the bearing 36 in the leg portion 37.
The element tube 11 wound in a coil shape is deformed into a flat shape by contact between the element tubes. If drawing is performed in a deformed shape, the flat element tube 11 does not come into uniform contact with the drawing die 24 and buckles due to application of twist. Accordingly, the roundness is drawn with a reduction ratio of 0.5 to 3% so that the ratio of major axis / minor axis is within 1.2. The diameter reduction ratio is obtained by (percentage of the outer diameter of the raw pipe 11 before drawing−the outer diameter of the inner spiral grooved pipe after drawing) / the outer diameter of the raw pipe before drawing.

The drawing die 24 is disposed on the axis C1 so as to pass the raw tube 11 just after being unwound from the unwinding side capstan 22. Specifically, the drawing-side capstan 25 is arranged in a state where the running path of the unwinding-side capstan 22 and the raw tube 11 is aligned with the axis C1, and the drawing die is placed between the capstans 22 and 25. 24 is arranged. The extraction-side capstan 25 is rotated by a motor drive by the motor device M1. In this case, the extraction-side capstan 25 is supported by the gantry 42, and the extraction die 24 is also integrally fixed to the front end portion of the gantry 42.
Similarly to the unwinding side capstan 22, the drawing side capstan 25 includes a driven roller 43, and the inner side spiral grooved tube 11 </ b> R is wound around the driven roller 43 so as to be wound around a plurality of turns. As a state, it sends out in parallel with the axis C1. The inner spiral grooved tube 11R is wound around the capstan 25 for several turns. In the drawing-side capstan 25, the inner spiral grooved tube 11 </ b> R is fed out of a direction parallel to the rotation axis of the capstan 25 with respect to the axis C between the capstans 22 and 25.

  Also in this case, the driven roller 43 is provided at a position retracted from the axis C1 (travel path of the inner surface spiral grooved tube 11R), and the axis C1 (with inner surface spiral groove) with respect to the drawing-side capstan 25. It is arranged so as to be perpendicular to the travel path of the pipe 11R. Therefore, the space between the drawing-side capstan 25 and the upstream unwinding-side capstan 22 is narrowed, and the twisted region of the blank tube 11 therebetween is shortened, thereby effectively suppressing the occurrence of buckling. can do.

  As shown in FIG. 4, the drawing die 24 has a die hole 24 a through which the element tube 11 is inserted, and performs empty drawing to reduce the outer diameter of the element tube 11. The diameter reduction rate in the drawing die 24 is 5 to 40%. When the diameter reduction ratio is too small, the effect of drawing is poor, and it is difficult to obtain a large twist angle, so it is preferable to set it to 5% or more. On the other hand, if the diameter reduction ratio is too large, breakage tends to occur at the processing limit, so 40% or less is preferable.

  Further, in this embodiment, a third capstan 27 supported by the gantry 44 is provided at a downstream position of the extraction side capstan 25, and between the extraction side capstan 25 and the third capstan 27. A second drawing die 26 is provided. The third capstan 27 is rotated by a motor drive by the motor device M2. The second drawing die 26 is provided for the skin pass of the inner spiral grooved tube 11R formed by passing through the previous drawing die 24, and the cross-sectional change due to drawing is small, and the surface and dimensions are finished. While being shaped, the roundness of the inner spiral grooved tube 11R is restored.

The configuration of the third capstan 27 is the same as that of the other capstans 22 and 25 described above, and the inner spiral grooved tube 11R is unwound in a state of being wound around the driven roller 45 so as to be wound around a plurality of turns. It is. The driven roller 45 is disposed so as to be retracted from the axis C (traveling path of the inner spiral grooved tube 11R), and is located on the axis C (traveling path of the inner spiral grooved tube 11R) with respect to the third capstan 27. The point arrange | positioned so that it may become perpendicular | vertical is the same as that of the other driven rollers 41 and 43. FIG.
The winding drum 29 winds the inner spiral grooved tube 11R with a constant tension, and includes a drive unit 46 for rotation.

Next, a method of manufacturing the inner spiral grooved tube 11R using the manufacturing apparatus A configured as described above will be described.
As shown in FIG. 5, a raw tube (extruded raw tube) 11 in which a plurality of linear grooves 11 a along the length direction are formed on the inner surface at intervals in the circumferential direction is prepared in advance by extrusion (raw tube extrusion). Process).

The base tube 11 used in the present embodiment has a bottom wall thickness of 0.55 mm to 0.9 mm. The element tube 11 is a fibrous structure in which the metal structure is all along the length direction of the tube, or 5% or less of the thickness of the surface layer is a recrystallized structure on the outer periphery and the inner periphery, respectively. Other than the above, all are made into a fibrous structure or a crystal grain having a whole surface average crystal grain size of 80 μm or less.
The base tube 11 having the metal structure and the groove shape can be manufactured by controlling the extrusion speed and the temperature in the billet of the extrusion apparatus. The extrusion speed is controlled by controlling the temperature at which the aluminum material is charged into the extrusion apparatus at 540 to 560 ° C. under the production conditions where the extrusion speed is controlled to about 40 m / min. It means heating at about 595 ° C. for several hours to 10 hours.
By extruding under the above-mentioned conditions, the metal structure and shape of the aluminum alloy constituting the base tube 11 is such that the bottom wall thickness of the base tube is 0.55 mm or more and 0.9 mm or less, and all the metal structures are the length of the tube. It is possible to control the fibrous structure along the length direction or the surface layer only to 5% or less of the inner and outer peripheral wall thicknesses of the recrystallized structure, and to control all the others to the fibrous structure or the crystal grains having an overall average grain size of 80 μm or less. it can. Increasing the material input temperature or increasing the extrusion rate to increase the heat generated by processing increases the crystal grain size, which is not desirable.

  The raw tube 11 having the metal structure described above is held in a coil shape on the unwinding drum 21, and the raw tube 11 unwound from the unwinding drum 21 is wound around the unwinding side capstan 22 while rotating. 23, the unwinding drum 21 and the unwinding side capstan 22 are rotated around the axis C by integrally rotating with the frames 32 and 38 to unwind the unwinding tube 11 from the unwinding side capstan 22 (the unwinding tube). Unwinding process).

The unwound raw tube 11 is passed through the drawing die 24 and then wound around the drawing-side capstan 25, whereby the raw tube 11 is drawn to reduce the diameter (raw tube drawing step). By this raw tube drawing step, the raw tube 11 is twisted, and the inner surface spiral grooved tube 11R in which a spiral groove is formed on the inner surface is obtained.
In this case, twisting causes a shear stress to act on the element tube 11 in the circumferential tangential direction and imparts a torsion angle. At the same time, a compressive stress associated with the twist acts in the longitudinal direction of the element tube 11, and the value is The buckling occurs when the bending stress is exceeded, but the compressive stress can be reduced by the tensile stress in the longitudinal direction of the pipe by the drawing process, so that the occurrence of buckling can be suppressed.

Since the base tube 11 or the inner spiral grooved tube 11R is wound around the capstans 22 and 25 before and after the drawing die 24, the drum centering shaft C1 and the final drum winding shaft and the axis C1 of the machining area where the twist is applied. Is displaced in a direction parallel to the rotation axis of the capstan 22 by the number of circumferences of the raw tube 11 wound around the unwinding side capstan 22, and is wound and restrained by the front and rear capstans 22 and 25, thereby As shown in FIGS. 2 and 4, the processing zone length 11 can be controlled at a constant distance L from the top position of the unwinding side capstan to the position of the final end of the drawing die. The longer the working area, the smaller the buckling stress. As a result, buckling is likely to occur even with a slight twist. Therefore, the distance between the capstans 22 and 25 should be adjusted as short as possible. Thus, even when a large twist angle is given, the occurrence of buckling can be suppressed.
If the position of the drawing side capstan 25 is too far from the terminal end of the drawing die 24, the inner spiral grooved tube 11R is wound around the capstan 25, but the restraining force is weakened, and the drawing die 24 turns into the inner spiral groove. Even after the attached tube 11R comes out, the inner spiral grooved tube 11R rotates. In this case, the length of the machining area changes in the longitudinal direction, which causes the twist angle in the longitudinal direction to vary.

If the distance between the capstans 22 and 25 is too small, the capstans 22 and 25 come into contact with the gantry 42 that supports the drawing die 24. The diameters of both capstans 22 and 25 are preferably 100 mm or more. If it is less than 100 mm, there is a possibility that the raw tube will buckle or flatten when wound around the respective capstans 22 and 25. On the other hand, if the distance is 900 mm or more, as described above, the distance between the capstans 22 and 25 is too large, and buckling is likely to occur.
The twist angle of the inner spiral grooved tube is determined by the relationship between the revolution speed of the unwinding side capstan 22 and the unwinding speed of the element tube 11.

The inner spiral grooved tube 11 </ b> R formed by this drawing process is unwound from the drawing-side capstan 25 and wound around the third capstan 27, and the second drawing die 26 is interposed between these capstans 25, 27. The surface is shaped by inserting the inner spiral grooved tube 11R (finish drawing step). Even if the inner spiral grooved tube 11R has undergone some deformation such as crushing in the raw tube drawing process, the deformation is also corrected by passing through the finish drawing process, and the inner spiral groove having a predetermined roundness is obtained. The auxiliary tube 11R can be used.
Finally, the inner spiral grooved tube 11R is wound around the winding drum 29 (winding step).
The take-up drum 29 is rotated by a motor drive in synchronization with the drawing-side capstan 25 and the capstan 27.

  As described above, by pulling while rotating the raw tube 11 in a state in which a constant tension is applied between the unwinding side capstan 22 and the drawing side capstan 25, a large amount of buckling is not caused. The inner spiral grooved tube 11R having a twist angle can be manufactured. In particular, since there is no need to perform a rolling process with a plug or the like inside, by forming a fin 11b having a small apex angle on the inner wall of the raw tube 11 in advance during extrusion, the fin 11b is crushed. The raw tube 11 can be twisted without any problem, and the slim fin type inner spiral grooved tube 11R can be manufactured, and the inner surface of the tube material is not particularly required to be cleaned after processing.

  Further, in the above-described manufacturing process, a constant tension is applied to the raw tube 11 when the twist is applied by the rear tension by the brake device 15 and the front tension by the rotational torque control of the motor device M2. Thereby, it becomes possible to apply a twist while applying a constant tension in a processing region from the unwinding side capstan 22 to the drawing die 24, and a constant twist angle can be given to the element tube 11. More specifically, the variation in the twist angle of the groove of the inner spiral grooved tube 11R can be made ± 1 ° or less (ie, the variation is ± 1 ° or less) from the target value.

The inner surface spiral grooved tube 11R obtained in the above-described process has good forming accuracy of the spiral fin 11e, and even when the long inner surface spiral grooved tube 11R is manufactured, it is uniform in its length direction. It is possible to obtain the inner spiral grooved tube 11R provided with the helical fin 11e having a large twist angle, fin height, fin apex angle, and fin apex width.
If a heat exchanger is assembled using the internal spiral grooved tube 11R provided with the high-precision spiral groove 11d and the spiral fin 11e as described above, a high-performance heat exchanger with good heat exchange efficiency can be provided.

Further, the inner spiral grooved tube 11 </ b> R is manufactured using the raw tube 11. The base tube 11 has a bottom wall thickness of 0.55 mm to 0.9 mm. Thereby, the bottom wall thickness d of the manufactured inner surface spiral grooved tube 11R can be set to 0.55 mm or more and 0.9 mm or less.
Further, in the raw tube 11, the height of the fin 11b on the inner surface is 0.24 mm or more, and the fin apex angle represented by the relative angle between the two side wall surfaces of the fin when the fin 11b is cut is 25 ° or less. It is said that. The shape of the inner fin does not change significantly before and after the twist is applied. Therefore, the height t of the fin 11c of the inner surface spiral grooved tube 11R can be 0.24 mm or more, and the fin apex angle θ ₁ can be 25 ° or less.

In addition, the inner spiral grooved tube 11 </ b> R is manufactured using the raw tube 11. The base tube 11 is a fibrous structure in which the metal structure is all along the length direction of the pipe, or 5% or less of the thickness of the surface layer is the recrystallized structure on the outer periphery and the inner periphery, respectively. All of them are fibrous structures or crystal grains having an overall average crystal grain size of 80 μm or less. Since there is no generation of orange peel after production because it is produced using such a raw tube 11, and the average crystal grain size of the inner surface spiral groove tube after annealing for making O material is 120 μm or less, Even if the pipe is expanded, an orange peel is not generated, and it is possible to provide a pipe with an inner surface spiral groove that has excellent pipe expandability that hardly causes fin collapse and that has a high joining ratio with the radiation fin.
In addition, the inner surface spiral grooved tube 11R obtained after the processing is work-hardened, and as it is, the hardness is high, and the tube expansion by the tube expansion plug is hindered. Therefore, it is softened by performing annealing for O material, Easy to expand. O-materialization by annealing means a process of heating the inner spiral grooved tube 11R in a temperature range of 300 to 420 ° C. for 0.5 hours or more and within 4 hours and then gradually cooling.
If the heating temperature at the time of forming the O material is less than 300 ° C., the tube after processing cannot be completely distorted, and if the heat treatment is longer than 4 hours, crystal grains may grow too much, leading to the generation of orange peel. is there.

  Further, by generating a certain twist in the raw tube 11, it is possible to form the inner spiral grooved tube 11R having a small diameter and a large twist angle θ. By increasing the twist angle of the groove, the internal surface area through which the refrigerant flows can be increased, and the thermal characteristics are improved. Further, by making the diameter small, the degree of freedom in designing the heat exchanger can be increased, contributing to downsizing, and it becomes possible to arrange the small-diameter heat transfer tubes at a high density.

FIG. 7 is a schematic view showing an example of a heat exchanger 80 provided with an inner surface spiral grooved tube according to the present invention, and an inner surface spiral grooved tube 81 is provided meandering as a tube through which a refrigerant passes. A plurality of aluminum alloy fin members 82 are arranged around the grooved tube 81 in parallel. The inner surface spiral grooved tube 81 is provided so as to pass through a plurality of through holes provided so as to penetrate the fin material 82 disposed in parallel.
In the structure of the heat exchanger 80 shown in FIG. 7, the inner surface spiral grooved tube 81 includes a plurality of U-shaped main tubes 81A penetrating the fin material 82 linearly, and adjacent end openings of the adjacent main tubes 81A. A U-shaped elbow pipe 81B is connected as shown in FIG. Also, a refrigerant inlet 86 is formed on one end side of the inner spiral grooved tube 81 penetrating the fin material 82, and a refrigerant outlet 87 is formed on the other end of the inner spiral grooved tube 81. As a result, the heat exchanger 80 shown in FIG. 7 is configured.

A heat exchanger 80 shown in FIG. 7 is provided with an inner spiral grooved tube 81 so as to pass through the through holes formed in each of the fin members 82, and after being inserted into the through holes of the fin member 82, an inner spiral groove is formed by a tube expansion plug. The outer diameter of the attached tube 81 is expanded and assembled by mechanically integrating the inner spiral grooved tube 81 and the fin material 82.
By applying the inner surface spiral grooved tube 81 to the heat exchanger 80 shown in FIG. 7, it is possible to provide the heat exchanger 80 with good heat exchange efficiency.
Further, for example, when the heat exchanger 80 is configured using the inner spiral grooved tube 11R made of aluminum or an aluminum alloy, the outer diameter of the inner spiral grooved tube 11R is as small as 10 mm or less. Separation of the fin material 82 and the inner spiral grooved tube 81 is unnecessary, and a heat exchanger excellent in recyclability can be provided.

"Example 1"
An inner spiral grooved tube was manufactured using a 3003 aluminum alloy element tube having an outer diameter of 10 mm, an inner diameter of 9.1 mm, and a straight groove formed on the inner surface.
The raw tube is made of 3003 extruded material with an outer diameter of 10 mm and an inner diameter of 9.1 mm. The number of straight grooves on the inner surface is 45 (8 ° / 1 crest), and the height of the fin formed by these straight grooves is A 0.28 mm fin with a 10 ° apex angle was used. Using this blank, drawing was performed under the conditions of a drawing die hole diameter of 7.5 mm, a diameter reduction rate of 25%, and a drawing speed of 5 m / min.

First, when the relationship between the working area length and the revolution speed of the unwinding capstan was increased to examine the limit twist angle (the maximum twist angle that can be twisted without buckling), the results shown in FIG. 8 were obtained.
As shown in FIG. 8, there was a correlation between the two, and the value of the limit twist angle tended to increase exponentially as the machining zone length became shorter. This is reference data because the processing zone length of 180 mm does not lead to buckling.
The inner surface spiral grooved tube after the raw tube drawing process produced under the above conditions with a working zone length of 220 mm had an outer diameter of 7.5 mm and a spiral groove with a twist angle of 30 ° formed on the inner surface. After the finishing drawing process, the twist angle is slightly reduced by passing the third drawing die, so that the outer diameter is 7.2 mm and the twist angle of the inner spiral groove is 28 °. .
In addition, using a 3003 aluminum alloy element tube with an outer diameter of Φ10 and an inner diameter of Φ9.1 provided with straight grooves on the inner surface, the revolving speed of the unwinding side capstan is set at a processing zone length of 220 mm and a drawing speed of 5 m / min. As a result of examining the influence of the diameter reduction ratio at the time of drawing on the limit twist angle (the maximum twist angle that can be twisted without causing buckling), the results shown in FIG. 9 were obtained.
As shown in FIG. 9, there is a correlation between the two, and the tendency that the limit twist angle increases as the diameter reduction ratio at the time of drawing increases is recognized.

Next, a twisted angle at the time of drawing and the unwinding side using the apparatus shown in FIG. 1 using a blank tube made of 3003 aluminum alloy having an inner diameter φ = 10 mm and an inner diameter φ = 9.1 mm provided with a linear groove on the inner surface As a result of examining the relationship between the rotation speeds of the frames, the results shown in FIG. 10 were obtained.
FIG. 10 shows the relationship between the twist angle and the unwinding-side capstan rotation speed under the conditions of a machining area length of 220 mm, 30% reduction, an outer diameter of φ7.5 mm, an inner diameter of φ6.6 mm, and a drawing speed of 10 m / min.
It has been found that the rotational speed of the unwinding side frame and the twist angle are in a proportional relationship, and that the twist angle can be varied by varying the rotational speed of the unwinding side frame.

"Example 2"
Next, using a device tube made of 3003 aluminum alloy having an outer diameter φ = 10 mm and an inner diameter φ = 9.1 mm provided with a straight groove on the inner surface, the processing area length 220 mm, 30% using the apparatus shown in FIG. Reduction, pulling speed 10 m / min, unwinding side capstan revolution speed 180 rpm, outer diameter φ7.5 mm, inner diameter φ6.6 mm, inner diameter spiral groove of 20 ° inner diameter groove of 778 m A tube was manufactured. A part of the inner spiral grooved tube was cut out over a length of 5 m, and the twist angle distribution in the length direction of the cut inner spiral grooved tube was examined. The result is shown in FIG.
From the results shown in FIG. 11, the inner surface spiral grooved tube formed using the manufacturing apparatus shown in FIG. 1 was able to give a stable twist angle in the longitudinal direction. Further, the variation in the twist angle was within a range of ± 0.5 °, and it was found that a uniform twist angle could be imparted in the longitudinal direction of the pipe material with extremely excellent accuracy.

Reference example
Next, an element pipe made of 3003 aluminum alloy having an outer diameter φ = 10 mm and an inner diameter φ = 9.0 mm with a linear groove on the inner surface is used, and a length having an inner spiral groove of 25 ° using the apparatus shown in FIG. An internal spiral grooved tube having a length of 778 m was produced. In this production, a twisted tube having a drawing reduction of 30%, a processing zone length of 220 mm, and an outer diameter of 7 mm was produced under the conditions of a drawing speed of 10 m / min and a revolving speed of the unwinding side capstan of 250 rpm.
For the internal spiral grooved tube having a length of 778 m, the twist angle (°), the outer diameter (mm), the bottom wall thickness (mm) at each position of 10 m, 195 m, 389 m, 584 m, and 775 m in the length direction from the processing start position. ), Fin height (mm), fin apex width (mm), and fin apex angle (°) are shown in Table 1 below.
The fin apex angle θ ₁ is an angle formed by the left and right hypotenuses in the isosceles trapezoidal fin shown in FIG. 12, and the fin apex width is the width of the fin apex portion. The fin height was the height from the fin bottom to the fin top.
The bottom wall thickness d indicates the wall thickness of the inner spiral grooved tube 11R corresponding to the spiral groove 11d as shown in FIG. Since the inner spiral grooved tube 11R is circular in cross section, it is measured as a height t connecting the center point of the bottom side of the fin 11c and the center point of the top side of the fin 11c as shown in FIG. .
In addition, a tube was cut out from each measurement position portion of the obtained inner surface spiral grooved tube over a length of 140 mm, and the cut-out tube was used as a test piece as it was, and TS (tensile strength), YS (yield strength), EL ( Elongation) was measured.

From the test results shown in Table 1, even if the inner spiral grooved tube manufactured by the apparatus shown in FIG. 1 is an inner spiral grooved tube having a length of about 778 m, the torsion angle and outer diameter are uniform in the length direction. It is clear that the bottom wall thickness, fin height, fin apex width and fin apex angle are shown. The twist angle was within a range of ± 0.5 ° with respect to the target angle of 25 °.
Further, it can be seen that the obtained internally spiral grooved tube has a small variation in TS, YS, and EL in the length direction and is uniformly processed.

Example 4
Next, an inner spiral grooved tube was manufactured by the same manufacturing method as described above using a 3003 aluminum alloy base tube having an outer diameter of 10 mm, an inner diameter of 8.86 mm, and a linear groove formed on the inner surface. The inner diameter means the diameter of a circle on the inner surface drawn by connecting the bottoms of grooves (straight grooves or spiral grooves).
The raw tube is an extruded raw tube manufactured by carrying out a billet homotreatment for 5 hours at an extrusion rate of 40 m / min, an extrusion apparatus billet temperature of 550 ° C. and a billet homo treatment temperature of 580 ° C. for 5 hours as the production conditions during extrusion. It is.
The number of straight grooves on the inner surface is 36 (36), the height of the fin formed by these straight grooves is 0.26 mm, and the apex angle of the fin is 10 °. The average diameter of the blank is 80 μm. Of crystal grains.
Moreover, although the fin shape etc. are equivalent, the raw tube which has a crystal grain structure | tissue whose average crystal grain size is 140 micrometers was used as a raw tube of a comparative example. The raw tube of this comparative example is an extruded raw tube manufactured under the conditions of an extrusion speed of 40 m / min, an extrusion apparatus billet temperature of 520 ° C. when an aluminum material is charged, and a billet homotreatment that is held at 610 ° C. for 8 hours.

Using such an element tube, an internally spiral grooved tube having an outer diameter of 4 mm, a twist angle of 20 °, a fin apex angle of 10 °, a fin height of 0.26 mm, and a bottom wall thickness of 0.6 mm could be manufactured. .
The inner surface spiral grooved tube obtained by the above process was heat-treated at 350 ° C. for 4 hours for tube expansion. FIG. 14 (a) shows an enlargement of the metal structure of a partial cross section of the internally spiral grooved tube obtained by using a raw tube having a crystal grain structure with an average grain size of 80 μm. A part of the internally spiral grooved tube is shown in FIG. 14 (b) shows a state in which the inner surface is cut open, FIG. 14 (c) shows a state in which the inner surface spiral grooved tube is cut obliquely, and FIG. d).

  FIG. 15 (a) shows an enlargement of the metal structure of a partial cross-section of the internally spiral grooved tube obtained by using a raw tube having a crystal grain structure with an average crystal grain size of 140 μm in the same manufacturing method as described above. FIG. 15B shows a state in which a part of the inner surface spiral grooved tube is cut open, and FIG. 15C shows the groove shape of the cross section of the inner surface spiral grooved tube.

In the inner spiral grooved tube of the example shown in FIG. 14, the shape of fins formed between the obtained spiral grooves and the grooves was uniform, and the fins and spiral grooves of the desired shape could be formed. Moreover, rough skin such as orange peel could not be observed on the surface of the inner spiral grooved tube.
On the other hand, the inner surface spiral grooved tube of the comparative example shown in FIG. 15 has irregular fin shapes, such as a part of the fins being bent. Further, as shown in the structural photograph of FIG. 15 (a), the crystal grains are large, and the crystal grains form part of the grooves and the fins. Therefore, some of the crystal grains fall off and some of the fins are missing. I was able to confirm multiple locations. Moreover, rough skin was confirmed as orange peel on the surface.

FIG. 16 is a diagram showing a comparison of the surface states of the inner surface spiral grooved tube of the example and the inner surface spiral grooved tube of the comparative example, and the inner surface obtained in the example as shown in FIG. The spiral grooved tube shows no smooth surface condition with no orange peel. On the other hand, as shown in FIG. 16 (b), the internal spiral grooved tube of the comparative example generated orange peel, and the surface was rough.
From the above comparison, it is clear that the inner spiral grooved tube obtained by using a raw tube having a crystal grain structure with an average crystal grain size of 80 μm has a better fin shape and excellent surface properties. It is clear.

Separately, the inner spiral grooved tube having an outer diameter of 5 mm (inner diameter of 4 mm), an outer diameter of 4 mm (inner diameter of 3 mm), an outer diameter of 2.5 mm (inner diameter of 1.5 mm), and a twist angle of 20 °, is described above. It was confirmed that it could be produced through the same steps as in FIG.
Separately, prepare a tube with various adjustments of bottom wall thickness, fin apex angle, fin height, and twist it by the same process as described above to obtain various bottom wall thicknesses, fin apex angles, fin heights. It was confirmed that an internally spiral grooved tube having a thickness could be produced. Specifically, the bottom wall thickness was 0.55 mm, 0.65 mm, 0.75 mm, 0.85 mm. Also, fins having heights of 0.24 mm, 0.3 mm, 0.5 mm, and 0.8 mm were prepared. Moreover, the thing with a fin apex angle of 25 degrees, 15 degrees, and 5 degrees was produced.

Table 2 below shows the relationship between the size of the crystal grain size of the 3003 aluminum alloy used in the test, the homoprocessing conditions, and the extrusion conditions for the presence or absence of orange peel.
The presence or absence of orange peel occurred when the outer surface of the obtained spiral grooved tube with a length of 30 cm was observed with a microscope and no orange peel could be observed. I decided.

  As can be seen from Table 2, the generation of orange peel is suppressed in the spiral grooved tube using an elementary tube having an average crystal grain size of 80 μm or less or an elementary tube in which the crystal structure is a fiber structure.

  Next, an inner spiral grooved tube was produced by the same manufacturing method as described above using the elementary tube shown in Table 3 below, and the average crystal grain size (μm) in the state of the elementary tube of each sample, the inner spiral The average crystal grain size (μm) of the grooved tube, the presence or absence of orange peel generation, the average groove tilt angle (°) of the inner peripheral surface after processing, the tube expansion rate (%), and the surface roughness (Rmax) were measured and evaluated. . The tube expansion rate indicates the tube expansion rate before and after the tube expansion test (the denominator is before tube expansion).

Moreover, the cross section of the sample cut perpendicularly to the longitudinal direction of the inner spiral grooved tube was observed with a CCD camera, and the tilt angle of the fin was measured. Inclination angle theta ₂ of the fin, a straight line is drawn L1 across the fin base portions at both ends as shown in FIG. 13, and drawing a perpendicular line from the center b of the straight line L1 in the circle center direction (inner surface helical grooved tube center direction), The point where it intersects the top of the fin is c, and the angle abc is measured from the central part a of the top. For measuring the inclination of the fin, eight points were appropriately measured from each of the three fields of view of the inner spiral grooved tube cut out arbitrarily, and the average value of a total of 24 points was obtained.
In the four fins 11c shown in FIG. 13, the three fins 11c described on the left side are not deformed, and the fins on which one fin 11c described on the right side is deformed are illustrated. Since the right side of the fins 11c of FIG. 13 is deformed, the fins inclination angle theta ₂ becomes 0 °. Note that FIG. 13 is drawn to illustrate the fin apex angle, and usually fin collapse occurs in the plurality of fins 11c. Further, the fin apex angle θ ₁ is shown in FIG. 13 for reference.

The tube expansion test was performed by attaching a tube expansion plug to the chuck portion of a 100 kN tensile tester and inserting the tube expansion plug into the inner spiral grooved tube 11R. In the pipe expansion test, RF-520 manufactured by NSL Bricantz Co., Ltd. was used as the lubricating oil between the inner peripheral surface of the inner spiral grooved tube 11R and the pipe expansion plug 76. As the tube expansion plug, a plug made of cemented carbide having an outermost diameter portion of 5.9 mm was used. The insertion speed of the tube expansion plug 76 was 285 mm / min.
In the pipe expansion test of the inner spiral grooved tube, the inner spiral grooved tube obtained in the example was subjected to heat treatment (annealing) at 350 ° C. for 4 hours.

Moreover, about each inner surface spiral grooved tube, it observed visually whether the orange peel had generate | occur | produced on the outer peripheral side. The presence or absence of orange peel occurred when the outer surface of the obtained spiral grooved tube with a length of 30 cm was observed with a microscope and no orange peel could be observed. I decided. Details of the evaluation method are as described above. The test results for each sample are shown in Table 3 below.
Moreover, about the outer periphery of the obtained internal spiral grooved pipe, the surface roughness (Rmax) was measured with a two-dimensional roughness meter (Surfcom 1400D: Tokyo Seimitsu Co., Ltd.). For parameter calculation, the JIS '94 standard was selected, the least square straight line correction was added, the sample inclination was canceled, the measurement length was 4 mm, the measurement speed was 0.3 mm / s, and the measurement range was ± 400.0 μm.

  Table 3 below shows whether or not the orange peel is generated with respect to the average crystal grain size of the raw tube used in the test and the internally spiral grooved tube after the heat treatment.

Based on the results shown in Table 3, the raw material (sample Nos. 1, 2, and 3) having a full-face fiber structure, double-sided surface layer 3% recrystallization (remaining fiber structure), and double-sided surface layer 5% recrystallized structure (remaining fiber structure) is used. Then, it was possible to reduce the average crystal grain size to 80 μm or less (for example, 60 μm or less) for the internally spiral grooved tube after processing. In these samples, no orange peel was observed, and the fin collapse angle could be controlled to 0.4 ° or less.
For these samples, no. Samples 4, 5, and 6 were samples with an average crystal grain size exceeding 80 μm or samples with a double-sided surface layer of 8% recrystallized structure. Orange peel was observed, and the fin collapse angle increased beyond 1 °. It was.
When the fin collapse angle is large, when the heat exchanger is assembled by expanding the inner spiral grooved tube with a tube expansion plug, the inner surface fin that the tube expansion force exerted by the tube expansion plug collapses is more easily acted. If it will be in this state, as a result of deform | transforming so that an inner surface fin may fall down further, the expansion of an inner surface spiral grooved tube will become insufficient, and manufacture of a heat exchanger will be hindered. For example, when the heat exchanger is composed of an inner spiral grooved tube and an external fin, the inner spiral grooved tube is inserted into a through-hole formed in the outer fin, and the inner spiral grooved tube is expanded. Although the exchanger is assembled, if the tube expansion is insufficient, the adhesion between the external fin and the inner spiral grooved tube is inferior, and the heat exchange performance is deteriorated.

"Comparative Example 1"
An internally spiral grooved tube was manufactured by a groove rolling method using a 3003 aluminum alloy tube.
An internally grooved tube made of 3003 aluminum alloy having an outer diameter of 10 mm, a fin apex angle of 20 °, and a fin height of 0.28 mm was manufactured by the groove rolling method using the apparatus shown in FIG. The inner spiral grooved tube shown in FIG. The inner surface spiral grooved tube shown in FIG. 18 is clearly broken in the shape of the fin as represented by the portion surrounded by a round frame, indicating that high-precision machining has not been achieved.

  Although various embodiments of the present invention have been described above, each configuration in each embodiment and combinations thereof are examples, and addition, omission, replacement, and configuration of configurations are within the scope not departing from the spirit of the present invention. And other changes are possible. Further, the present invention is not limited by the embodiment.

A Manufacturing device 11 of inner surface spiral grooved tube Elementary tube 11a Linear groove 11b Fin 11R Inner surface spiral grooved tube 21 Drum (unwinding drum)
21a Winding shaft 22 Unwinding side capstan 23 Rotating means 24 Pulling die 24a Die hole 25 Pulling side capstan 26 Second pulling die 27 Third capstan 29 Winding drum 31 Guide pulley 32 Frame (first frame)
38 Second Frame C Axis (Axis of Rotating Means)
C1 axis (axis of machining area)

Claims (22)

A plurality of linear grooves along the length direction are formed in the inner surface at intervals in the circumferential direction, and the inner surface is manufactured by directly twisting an aluminum tube in which fins are formed between the linear grooves. A spiral grooved tube,
The bottom wall thickness of the inner spiral groove tube in the plurality of spiral grooves is 0.55 mm or more;
The height of the fin from the spiral groove is 0.24 mm or more;
The fin apex angle represented by the relative angle of the two side wall surfaces of the fin when the fin is sectioned is 25 ° or less,
In the grain structure, the average grain size is 120 μm or less,
The inner spiral grooved tube characterized in that the variation in twist angle of the groove varies within a range of ± 1 ° or less in any measurement range of 1 m to 5 m in length .   2. The inner spiral grooved tube according to claim 1, wherein the bottom wall thickness is 0.65 mm or more.   The inner spiral grooved tube according to claim 1 or 2, wherein a height of the fin is 0.5 mm or more. The inner spiral grooved tube according to any one of claims 1 to 3, wherein the element pipe is an extruded element pipe having a bottom wall thickness of 0.55 mm to 0.9 mm. A plurality of linear grooves along the length direction are formed in the inner surface at intervals in the circumferential direction, and the inner surface is manufactured by directly twisting an aluminum tube in which fins are formed between the linear grooves. A spiral grooved tube,
The outer diameter is 5mm or less,
The twist angle of the groove is 20 ° or more and 40 ° or less,
In the grain structure, the average grain size is 120 μm or less,
The inner spiral grooved tube characterized in that the variation in twist angle of the groove varies within a range of ± 1 ° or less in any measurement range of 1 m to 5 m in length . The inner spiral grooved tube according to any one of claims 1 to 5 , wherein a variation in bottom wall thickness is ± 1% or less. The inner spiral grooved tube according to any one of claims 1 to 6 , wherein variation in outer diameter is ± 1% or less. The inner spiral grooved tube according to any one of claims 1 to 7 , wherein the average grain size of 120 µm or less is an average grain size achieved after annealing. The tube with an inner surface spiral groove according to any one of claims 1 to 8 , wherein a fin inclination angle of the fin formed along the inner surface spiral groove is 1 ° or less. The inner surface spiral grooved tube according to any one of claims 1 to 9 , wherein the outer surface has no orange peel defined as a step exceeding a surface roughness (Rmax) of 15 µm. In the inner spiral grooved tube, about the crystal grain structure of the raw tube used for its production,
The metal structure is all the fibrous structure along the length of the tube, or the surface layer only has a recrystallized structure with 5% or less of the outer and inner wall thicknesses, and the rest is all the fibrous structure, or the average of the metal structure The inner spiral grooved tube according to any one of claims 1 to 10 , wherein a crystal grain size is 80 µm or less. A plurality of linear grooves along the length direction are formed on the inner surface at intervals in the circumferential direction, and an aluminum base tube in which fins are formed between the linear grooves is unwound from a drum holding the coil. By rotating the drum and the unwinding side capstan along the axis perpendicular to the winding axis of the drum while being wound around the side capstan, the raw tube is rotated around the axis from the unwinding side capstan. An unwinding process of unrolling the unwound pipe, and a twisting and unwinding process of passing the unwound unwound pipe through a pulling die and applying a twist while reducing the diameter to form an internally spiral grooved tube,
The straight groove is a spiral groove, the fin is spiral, the bottom wall thickness of the plurality of spiral grooves is 0.55 mm or more, the height of the fin from the spiral groove is 0.24 mm or more, and the fins The fin apex angle represented by the relative angle between the two side wall surfaces of the fin when the cross section is taken is 25 ° or less, the average grain size is 120 μm or less in the crystal grain structure, and the twist angle of the groove varies. A manufacturing method of an internally spiral grooved tube characterized by being ± 1 ° or less. 13. The method for manufacturing an inner surface spiral groove tube according to claim 12 , wherein a raw tube having a bottom wall thickness of 0.55 mm or more and 0.9 mm or less is used to manufacture the inner surface spiral groove tube. A plurality of linear grooves along the length direction are formed on the inner surface at intervals in the circumferential direction, and an aluminum base tube in which fins are formed between the linear grooves is unwound from a drum holding the coil. By rotating the drum and the unwinding side capstan along the axis perpendicular to the winding axis of the drum while being wound around the side capstan, the raw tube is rotated around the axis from the unwinding side capstan. An unwinding process of unrolling the unwound pipe, and a twisting and unwinding process of passing the unwound unwound pipe through a pulling die and applying a twist while reducing the diameter to form an internally spiral grooved tube,
The straight groove is a spiral groove, the fin is spiral, the outer diameter is 5 mm or less, the twist angle of the groove is 20 ° or more and 40 ° or less, and the average grain size is 120 μm or less in the crystal grain structure. A method for producing a spiral grooved tube having an inner surface. As the element tube, the metal structure is all a fibrous structure along the length direction of the tube, or the surface layer has a recrystallized structure of 5% or less of the outer and inner circumferences, and the rest are all a fibrous structure. The method for producing an internally spiral grooved tube according to any one of claims 12 to 14 , wherein an extruded element tube having an average crystal grain size of a metal structure of 80 µm or less is used. The method for producing an internally spiral grooved tube according to any one of claims 12 to 15 , wherein the diameter reduction rate by the drawing die is 5 to 40%. The position where the raw tube starts to be wound around the unwinding side capstan and the position where the raw tube starts to be fed from the unwinding side capstan to the drawing die side are shifted in a direction parallel to the rotation axis of the unwinding side capstan. The inner spiral grooved tube according to any one of claims 12 to 16 , wherein a space between the unwinding capstan and the drawing die is a twisted region of the raw tube. Production method. When diameter reduction while twisting the mother tube through the base pipe into the drawing die, the inner surface according to any one of claims 12 to 17, characterized in that the addition of forward tension and backward tension to the base pipe A method of manufacturing a spiral grooved tube. The method for producing an inner surface spiral grooved tube according to any one of claims 12 to 18 , wherein the inner surface spiral grooved tube that has passed through the drawing die is wound around a drawing side capstan. The method for producing an inner surface spiral grooved tube according to claim 19 , wherein the inner surface spiral grooved tube unwound from the drawing side capstan is shaped by a second drawing die. The inner spiral according to any one of claims 12 to 20 , wherein the raw tube unwound from the drum is shaped into a perfect circle by a drawing die before reaching the unwinding capstan. A method of manufacturing a grooved tube. A heat exchanger, wherein the inner spiral grooved tube according to any one of claims 1 to 11 and a fin are integrated.